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 Low tickover & high fuel consumption

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lcjohnny
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PostSubject: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 11:42 am

So my GRiSO has the beetle-map to suit its Termignoni pipe and feels very good on the road.

But it is very thirsty (33mpg english gals) and has a misfire at tickover.

Also the tickover is low 1000 to 1100 and the vaccum readings are not responsive to the air bleed scrws.

So does that sound like the gummed stepper motor issue or can the wise-men in the ghetto suggest any other answers?
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Pete Roper
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 12:36 pm

Is it running on one at idle? Does it break down at higher loadings?
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 1:53 pm

it runs on both with the occasional misfire - both cylinder heads stay within 5 degrees of each other.

It also seems fine at high loading. For example yesterday i had my wife on the back we were on the M5 which is quite hilly round here and  we were accelerating up the hills through 90mph with no hesitation at all


Last edited by lcjohnny on Sat Feb 27, 2021 4:50 pm; edited 1 time in total
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Pete Roper
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 2:33 pm

Did you clear the trims when you loaded the map? What is the CO trim set at?
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 4:50 pm

CO trim set at 0
TPS reset and 4.80
reset learning parameters done

I will recheck Co trim tomorrow as i understand if you are too quick it does not take and it used to be at -7 so i reset to 0 when i put the map in
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Oz1200Guzzi
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sat Feb 27, 2021 4:58 pm

Yes the engine needs to be > 60 degrees C, else it won't set.
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sun Feb 28, 2021 12:25 pm

well spotted Tony
the CO trim only got as far as -6

I will have to wait until the neighbours are out tomorrow to warm it up to 60 and get the CO down to zero.

Then i can see if it will respond to the air bleeds and give a better fuel consumption - in l per 100km I am only getting 8.5litres per 100km at present
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Pete Roper
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Sun Feb 28, 2021 12:52 pm

Yeah, definitely something wrong there, it's drowning in fuel!
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Thu Mar 04, 2021 3:49 pm

The first part of the fix was gummed up throttles.
Specifically the left air bleed was full of gum so was not adjusting,
After re-fittting it was easy to adjust the air bleed and the tickover came up from 1050 to 1180.

However at tickover every 10 seconds or so it stumbles - seems to miss a beat.
Could that be caused by a rich CO trim?

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Pete Roper
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Thu Mar 04, 2021 3:54 pm

Unlikely. That is usually a result of the throttle stop screw having been played with. That or the linkage rod length.
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Thu Mar 04, 2021 4:07 pm

I am hoping that the throttle stops and linkage rod have not been touched Sad

If they had been beggared about with i would be surprised to be getting close to identical vaccuum values at tickover (as well as on opening and rolling off the throttles.)

BtW It has new plugs (Desmo) leads and caps (NGK)
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paulbrice
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Fri Mar 05, 2021 1:14 am

Jon, mine used to 'stumble' on idle before rollerisation (revs would briefly dip). That went away after rollerisation (which could be anything but I thought valve clearances sorted) so I'm guessing it was balance/valves etc .... Although it hasn't ever returned enough to call it a 'stumble', I wouldn't say my idle is completely 'regular' so depends how big you call a stumble !

My TB linkages have never been tinkered...I thought vacuum balance is possible even if sacred screw has been turned; 'tinkering' messes up the factory throttle opening setting datum that map (fuelling etc) is built to operate with.
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Fri Mar 05, 2021 3:33 am

Well i may put up with the stumbling at idle - it is not enough for the revs to dip - maybe one firing stroke missed, possibly two every 10-15 seconds. It is such a joy to ride that my only concern now is to get the fuel consumption above mid-thirties.

However i understand that may be hard - years ago i had a Spada SP1000 usually did 45mpg but on one 100 mile ride against a friend with a LeMans ii  I got 28 mpg:pale:   but then again i never lost sight of him   Laughing

WE reckoned that the primitive fuel pumps on the Dell Orto VHB30s were not designed to be used like that Pillage!
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lcjohnny
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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Thu Mar 11, 2021 9:16 am

getting 40mpg = much better -
and i think the stumbling at idle may be a poor contact in the side stand switch as it kept moving between 0.7 and 85 ohms even after cleaning - think there is a problem in the wires immediately behind the switch
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lcjohnny
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lcjohnny

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PostSubject: Re: Low tickover & high fuel consumption   Low tickover & high fuel consumption Icon_minitime1Fri Jul 23, 2021 1:33 pm

updated now 48 mpg (English)
Result of fully tuning it with the beetle map & cleaning out the throttle bodies

and finally identifying that the rear brake was dragging - and stopping it
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